2001 CADILLAC SEVILLE STS

Typical onset: 80,000-120,000 mi

Symptoms: white smoke from exhaust, coolant loss with no visible leaks, overheating, coolant in oil (milky dipstick), rough idle and misfires

Fix: Northstar uses TTY head bolts that stretch and allow head gaskets to leak coolant into cylinders and oil passages. Proper fix requires removing heads, installing time-sert inserts into block threads, new head bolts, gaskets, and resurfacing heads. 18-24 labor hours if block is salvageable. Many shops quote engine removal for access.

Estimated cost: $3,500-6,000

Typical onset: 100,000-150,000 mi

Symptoms: knocking from lower engine, metal shavings in oil, catastrophic overheating event followed by noise, loss of oil pressure

Fix: When head gaskets fail and owner continues driving, coolant mixes with oil destroying bearings, washing cylinder walls, scoring pistons. Requires complete rebuild or replacement: short block, pistons, rings, bearings, machine work. 25-35 labor hours for full rebuild, often more cost-effective to swap in used engine.

Estimated cost: $5,000-9,000

Typical onset: 70,000-110,000 mi

Symptoms: transmission fluid leaking from radiator area, pink fluid puddles under car, transmission slipping or harsh shifts after fluid loss

Fix: Steel cooler lines running to radiator corrode and rupture, especially at crimped fittings. Replace both cooler lines preventively. 2-3 labor hours plus full transmission fluid flush and refill.

Estimated cost: $400-700

Typical onset: 90,000-130,000 mi

Symptoms: clunk when shifting from park to drive or reverse, excessive engine movement visible from engine bay, vibration at idle in gear

Fix: Hydraulic transmission mount fails internally, allowing drivetrain to move excessively. Replacement is straightforward but requires supporting engine/transmission. 1.5-2 labor hours.

Estimated cost: $300-500

Typical onset: 60,000-100,000 mi

Symptoms: ABS light illuminated, traction control disabled message, speedometer intermittent or erratic, stability control malfunction

Fix: Front wheel speed sensors corrode at connector or internally, causing ABS/traction faults. Diagnose with scanner, replace failed sensor. 1 labor hour per side.

Estimated cost: $200-350

Symptoms: hard starting when hot, stalling at idle after driving, loss of power under acceleration, fuel pump whine audible in rear seat

Fix: In-tank fuel pump strainer clogs from sediment, especially if tank has been run low repeatedly. Requires fuel tank drop, pump module replacement or cleaning. Often combined with pump replacement. 3-4 labor hours.

Estimated cost: $500-800